Information has been supplied on the so-called "pads for drum brakes" used on friction brakes, where there is a drum and at least one pad with its friction lining, lined for example. Upon applying a force on the pad or shoe, it actuates on the drum and by friction between the friction lining and drum the vehicle is brought to halt. The external shape of these shoes is of a general circular configuration and they are, as already mentioned, conventional elements used on all types of vehicles.
The conventional manufacturing processes of these vehicle shoes is well known and they are constituted by a core and wing made independently, which are adequately welded so as to form the final T shaped section of the shoe. The core and wing are machined so that they can serve as a base for the different mechanisms and as a linking nexus for others, and on the external surface of the wing, for example, there are lining plates through which the braking operation of the vehicle is performed.
During the operation of these shoes, several types of problems and failures arise, mainly originating from the weld tacks applied to join the wing and core, which on certain occasions cannot withstand too much stress and both elements fall apart with the subsequent uselessness of the clamp. Moreover, the manufacturing process is extremely cumbersome as it necessary to make a core with a series of holes, grooves . . . etc., depending on the brake model of the vehicle where it is to be applied, and also involves a wing produced from a flat iron, both of them being curved so that it is possible to superimpose the core over the wing, so as to weld both elements.
As mentioned before and apart from the constructive complexity, the application of welds originates certain problems, which are:
A practical impossibility of achieving a "perfect" weld between the core and wing.
A lack of uniformity in the distribution of the material used on the weld.
Internal material stresses upon welding.
A lack of a regular section in the shoe, as a tack welding procedure is used.
Lack of safety during the operation of the brake as the core and wing usually fall apart, with the subsequent risk for the vehicle's braking operation.
Within the present state of the art, there is U.S. Pat. No. 1,943,407 where a machine is detailed for the folding of T shaped sections, in an arched shape, where there is a roller, preferently formed by two joined-up parts, which form a groove between them where the T profile stem is located, and where the said T profile stem is maintained by friction against the walls of the said groove. In combination with this roller, there are also other peripheral rollers distributed around the main one where the head of the profile contacts when the main roller turns so as to gradully bend the profile and gradually adjust it more or less accurately, to the said main roller. This machine supplies a T section arched element, where the said arched T is obtained by successive bending actions by means of the peripheral rollers and in which the T that is obtained does not fit onto an axactly circular shape of its main roller (FIG. 12). The machine of this patent positions the ancillary rollers on the sole element that surrounds the main one and also contains a final stop (41') where it contacts with the T-shaped profile, already arched, so as to be extracted.
The assembly and constitution of this bending machine can eventually become expensive, and the T shaped profile does not modify its structure in a substantial manner from its initial straight shape until its final arched shape.
U.S. Pat. No. 2,047,084 is also known which, based on the knowhow of the aforementioned, mentions the existence of a recess on the external surface of the T shaped head, in its position directly opposite the T stem. In order to avoid this problem, Pat. 2,047,084 provides a method used to form brake shoes, whereby there is a main split rollers, with a groove or channel between both that applies pressure onto the stem of the T inside it, and another four rollers gradually bend the T shaped part in several successive stages, with the rollers maintaining the head of the said T fully clamped and also collecting portions of the main roller.
This system requires the existence of a main roller and of other bending rollers whose mission is to adjust the arched T to the main conductor roller in a complicated and costly layout.
U.S. Pat. No. 3,808,863 is also well known, which includes a method and a machine that rolls the entire contour of a T shaped section and which, in order to supply an arched T, has a bending roller (34) at the exit of the rolling assembly. The arched shape of the T section obtained does not fit onto any specific radius. The stem of the T is held between two rollers with a considerable amount of pressure and essentially executes two different and separate operations, one rolling and the other bending.
In the face of these techniques, the invention supplies a form of carrying out a base body for the production of shoes for brakes, which is economical, easy to assemble and simple to install.